Gear-adjusted variable resistor



GEAR-ADJ US TED VARIABLE RES IS TOR Filed NOV. 13, 1962 V, nk

INVENTOR. v l4f Meme 6. MA THISON 30 /4, /4 W United States Patent3,201,737 GEAR-ADXUSTED VARIABLE RESISTOR Victor G. Mathison, Riverside,(Ialih, 'assignor to Bourns, Inc, a corporation of California Filed Nov.13, 1962, Ser. No. 237,t122

- 16 Claims. (Cl. 338-174) The invention herein disclosed relates tovariable resistors, such as otentiometers, and more particularly tominiature single-turn variable resistors or potentiometers of thewormscrew-adjusted (gear-adjusted) type.

Variable resistors of the class to which the invention is applicable arecharacterized by an arcuate resistance element of somewhat less than 360extent, a wiper or contact capable of sweeping over the inter-terminalportion of the resistance element, andm'eans such as a shaft, forrotating the wiper or contact. Such potentiometers are of variousdimensions and configurations and are in most cases in excess ofone-half inch in minimum dimension in the plane of contact of theresistance element. The present invention makes possible the manufactureof a very small A" it Mr x A instrument of the class described withoutsacrifice of excellence in operating characteristics and withoutincreasing the cost of ,the instruments. According to the invention abase member for supporting the electrical components of thepotentiometer is formed, as by molding, of insulative material and so asto include, in situ and embedded in portions of the support, electricalterminal means. The terminal means are disposed for ready applicationand support of electrical components in readily accessible locations.The base member comprises a flat bottom portion and a walllike structureangularly disposed relative to the bottom and such that insertion of thebase member and its attached components into a strong open-endedbox-like member brings into proper juxtaposition the drivingcomponentsfor the instrument and completes an exceptionally strong andversatile housing or casing for the operating parts. The operatingmechanism comprises rotary means including a wheel-like member adaptedto be rotated by a suitable driver means and arranged to in turn impartrotation to a conductive contact device which includes a combined clutchmember or disc, clutch spring, slip ring or brush, and a wiper contactfor effecting connection to a selected intermediate part of a resistanceelement. The clutch disc of the contact device comprises a clutch facethat is engaged by the wheel-like member (which is hereinafter called agear wheel for the sake of convenience) and the gear wheel has acomplementary clutch face. The gear wheel has a series of long teeththat are disposed for engagement by the thread of a wormscrew orwormgear that acts as a driver for the rotary means of the resistor.

The box or cover member of the housing has mounted therein the drivingwormscrew, the latter being so disposed that the gear wheel is broughtinto proper engagement therewith when the base member is inserted intothe cover. After such insertion, the periphery along which the wall ofthe base member engages the cover is sealed. Thus provisions for closetolerances in relative positioning of the wormscrew and gear wheel areunnecessary, and the cost of producing the variable resistor is greatlyreduced from that obtaining when close tolerances in manufacture arerequired. It is evident that in making a device as small as thatpresented by the invention,

closetoleiances are extremely diflicult to attain due to the minutenessof the operating parts. Hence avoidance of parts and structures thatrequire close-tolerance manufacture is of considerable advantage inpermitting production of a less expensive device.

The preceding brief description makes it evident that ice a principalobject of the invention is to provide improvements resulting inreductions of cost of manufacturing a variable resistor of the classmentioned.

Another object of the invention is to provide an extremeiy small buteasily manufactured variable resistor.

Another object of the invention is to provide a variable resistor of theclass mentioned, which is immune to jamming and damage to parts when thedriver is overdriven.

An additional object of the invention is to provide a contact device fora potentiometer of the class mentioned, which contact device includes aresilient washer-like memher that serves concurrently as a clutchspring, a collector ring brush, and a contact support.

Another object of the invention is to provide a molded base structurewith embedded terminal means which greatly simplifies and facilitatesconstruction and provides for excellent contact termination of avariable resistor.

Other objects of the invention will be made evident in the appendedclaims and the following specification including the accompanyingdrawing in which:

FIGURE 1 is an isometric view, grossly enlarged, of an exemplaryphysical embodiment of the invention, with the base at the right of thefigure;

FIGURE 2 is a view in array of disassembled components of the variableresistor depicted in FIG. 1, to a still higher degree of enlargement,with sections of a housing component or cover broken away to illustratedetails.

FIGURE 3 is a sectional view taken as indicated by line 33 in FIG. 1,with sealant only partially applied;

FIGURES 4 and 5 are sectional views taken as indicated by lines 4-4 and55, respectively, in FIG. 3;

FIGURE 6 is a side view of a contact device formed by fusion-uniting twoof the components depicted in FIG. 2; and

FIGURE 7 is a face view of the bottom of a base member and terminal.

Referring first to FIG. 1, the variable resistor, in the form of apotentiometer, is designated generally by the ordinal 1%. As indicatedin FIG. 2, it comprises a boxlike housing means comprising an open-endedbox or cover 12 and a specially formed base member 14 which includes asubstantially flat bottom portion 1% and an integral upstanding wallportion 14w the outermost portion of which has a beveled interior facefor a reason and purpose presently to be explained. The base member 14is formed of thermosetting synthetic resin or other suitableelectrically insulative substance, and has molded integrally in thebottom portion 14b a wire-like terminal member 142. During the formationofthe base member by injection molding, a die operates to flatten aportion 14: of terminal wire 142 at and adjacent to the center of bottomportion 14b, as indicated in FIGS. 3 and 7. The die causes a circularcavity, 14c (FIG. 7) to be formed in the exterior face of bottom portion14b, in which cavity the flattened portion of the terminal wire 14! isexposed. The die displaces, slightly, the portion of the wire at andnear cavity Me as it flattens the wire against a flat surface of themold; and thus a flattened face of the wire is exposed at and flush withthe interior surface of bottom portion 14b of the base member asindicated in FIG. 2. These exposed surfaces of terminal member 141' areprovided for reasons presently to be explained.

Following molding of the base member 14, the latter is drilled atappropriate locations through ledges 1431, 142 formed on wall portion14w, for insertion of second and third terminal wires 14: and 14-), asindicated in FIG. 2. The latter wires are cemented in place with asuitable adhesive such as self-curing epoxy resin or the like; and arebent over against ledges 14y, 14z, as indicated in FIG. 2. Further, aconductive stub shaft or stud, 15, is fusion united in an accuratelydetermined position, to the flattened inner exposed face of wireterminal 142 (FIG. 3). The union may be effected by resistance welding,or by brazing. thus firmly secured to' base member 14 and in excellentelectrical communicationwith terminal wire 14L Stud '15 performs theplural functions of providing an electrical variable tap returnconductor for the variable resistor, of providing anaccurate positioningmeans for a resistance element, and a shaft upon which rotary means ofthe variable resistor are mounted.

In addition to ledges 14y, 14z, the wall portion MW of base member 14 isalso provided with an integral projection 14p which serves the severalfunctions of keying a resistance element in place, of providing a stopabutment for limiting the extent of rotation or traverse of rotarycontactfmeans that are mounted on stud 15 as hereinafter described, andof reinforcing the base member.

. A wafer=like resistanc'eielement, denoted generallyby numeralld (FIG.2), is shaped to fit around the base of stud 15 and flat against theinner face 14b of base member 14. Preferably the resistance element 16is permanently secured toface 14b by adhesive such as epoxy resincement. As indicated in the drawings, the resistance The circular baseof the stud 15 is. i

element comprises an insulative body or support lab that preferably isof ceramic material, anarcuate resistive means 16s supported on thebody, and terminal pads Ileq, 1dr that are electrically in contact withrespective end portions of. the arcuate resistive means. The resistivemeans is preferably but not necessarily a film of resistive metal-glasscomposition, that may be conveniently applied to the body or wafer andfired in a manner known in the ceramic arts. The terminal pads may besimilarly applied, as by, painting on appropriate areas of the Waferorgano-metal compound that is decomposed by heating to leave firmlyadherent low-resistance metal films. For example, platinum pads may beproduced by applying chloroplatinate solution and heating, as is wellknown in the ceramic art. Silver pads may be produced usingcomrnercially available silver paint. In either case, the pad' materialis applied so as to overlie or underlie each end portion of. the arcuateresistive means, according to whether the material is applied subsequentto, or prior to, application of the resistive means.

The resistance element 16 is of such configuration as to fit aroundthebase of stud l5, and is provided with an indentation or keyslot 16k. inwhich the lower part of projection 14p is received as indicated in FIG.5. A suitable adhesive, such as self-curing resin, is applied to thebottom of element 16 and the latter is pressed into place on the innersurface of base. 14b (FIG. 3). Thus the resistance element is accuratelypositioned and firmly secured in place. The element terminal pads areelectrically connected to respective ones of terminal Wires 14g, 141' bysuitable solder or other conductive adhesive, or by welding. As isindicated in FIG. 3, the inner ends of the wires are in close proximityto respective ones of pads 16g and 1dr on the resistive element, and aresoldered as at 14x to respective ones of the pads.

Disposed above element 16 and rotatable on stud 15 is a contact device18 that comprises an integral contactcarrying ring and combined springwasher and collector brush. A contact 180 (1 16.2) is formed on an ear18c protruding from a contact ring 18; that is integrally con-' nectedalong part of the inner edge to a resilient wavewasher 18wdisposedinside the ring. The wave washer has an elongate centralaperture one end of which is positioned adjacent the contact 180 and theother end. of which is near the area of-juncture diametrically oppositeear 180. Thus compression of the washer is permitted. Further the Washeraperture is somewhat larger in minimum diameter than the shaft of stud15, as indicated in FIG. 5, so precision in assembly with a clutch discpresently to be described) is not necessary. That much of thecontactdevice may be formed by punching froma fiat sheet of resilientconductive material such 'as berylliumpriately formed die means.Fusion-united to the upper side of the contact ring at an areadiametrically opposite the contact (see FIGS. 4-5) is a combined clutchdisc and stop member 18d hereinafter called a clutch disc, which is theupper element of the contact device 18. The clutch disc, as indicated inFIGS. 2, 3 and 4, has a central aperture which receives the upperreduced-diameter or shaft end of stud 15. Thus the contact device,including clutch disc 18d, spring washer 18w, and contact ring 1hr asintegrated components, is rotatable on stud T5. The

edgewise outline of the complete assembled contact device in the relaxedstate is depicted in FIG. 6. Rotatably mounted on stud 15 above thecontactdevic 18 is a wheel means or member 20 which is a combined clutchmember and gear formed preferably as a molded article of aself-lubricating material such as that marketed in commerce under thetrade name Nylatron. The lower face of the clutch and gear wheel member(hereinafter called gear wheel in the interest of convenience andbrevity) is constructed and arranged to frictionally engage and rotatethe clutch disc of the contact device in each of opposite directionsuntil such rotation is arrested by engagement of stop projection 14p bythe ear 18a provided on disc 13d. To that end, disc 18d is formed with aplurality of generally radial deformation such as 1311 whichdeformations are received in respective ones of a set of complementaryradial trough-like depressions Ztln between radially extendingprotuberances or ridge elements 20m formed on the lower face of gearwheel 20. The gear wheel is also provided with a series of gear teethsuch as Ztlg whereby it may be rotated by an engaging driver such as awormgear or wormscrew' presently to be described.

As is indicated in FIGS. 2 and 4, there is secured in and on the housingcover member 12, a driving or actuating means in the form of a wormscrew22 the thread 22 of which is constructed and disposed for drivingengagement with the teeth of gear wheel2il. Wormscrew 22 is providedwith .a tool-engaging driven end 2211 exposed for access from outsidethe cover, that end being provided with a formation (a screw-driver slotin the illustrated embodiment) suited for driving engagement by a toolsuch as a screwdriver or the like. The Wormscrew is journaled at itshead end in a stepped bore formed in the wall of cover member 12, and atits inner end 221 in a saddle bearing 12M fonmed integral with the coverat an interior. corner, as indicated in FIGS. 2 and 4. The worrnscrew isprovided with an O-ring seal 22d (FIG. 4) seated in a recess provided by.a step in the bore in'which it is journaled, whereby passage ofundesired substance through the bore is prevented. The wormscrew is prevented from accidental or unintentional removal from the housing by aretainer pin 22p (FIG. 4) .a first end of which is disposed in acircumferential groove 22g formed in the screw and the other end ofwhich is cemented in a hole or bore 121/ formed in a protrusion 12gformed to be integral withthe wall of the cover 12.

With the resistance element 16 affixed to surface 14b, and the rotarymeans comprising contact device 18 and gear wheel Ztldisposed on stud15, it is necessary to compress or stress to some extent the spring wavewasher 18w land the contact ring 181? before cover member 12 can bemoved over the subas s'embly, or the subassembly slid into the cover.With the wheel 2% pressed downwardly so that the resilient members arestressed, the base member 'and supported parts are moved into the coveruntil teeth of wheel 2t properly engage in the groove of the thread ofthe wormscrew, as illustrated in FIG. 3. Wall portion 14w is so formed(see FIGS. 4 and 5) that the inner portion thereof makes snug-fitengagement with the interior surfaces of the walls of cover 12, and thatportion is thick enough that the flange 14] does not contact the wallsof the cover. Thus close tolerances in means'controlling the spatiallocation of stud 15 relative to the axis of wormscrew ZZ-are notnecessary The'teeth of gearwheel 20 are sufficiently long thatengagement with the wormscrew at any of a plurality of locationstherealong is satisfactory; hence close dimensional tolerances onthickness of element 16, contact device 18 and the gearwheel need not beimposed. Similarly, close diametrical tolerances on the rotarystructures, and precision fits of rotary elements on stud 15, areunnecessary. Thus cost of manufacture of the parts is greatly lessened,and concurrently the assembly of the parts is greatly facilitated. Withthe base member 14 disposed within the cover member 12 and properinter-engagement of the thread 22! of the wormscrew with the toothedupper portion of the wormwheel assured by rotation of the screw, thecover member and base member are clamped together under light clampingforce and the peripheral groove 30 (FIGS. 3 and 4) between flange 14f ofthe base and the edges of the walls of cover 12 is filled with aself-curing adhesive sealant 32, as indicated in FIG. 1 and at the rightside only in FIG. 3.

It is to be noted that with the resilient components of the contactdevice stressed (as depicted in FIG. 3), the contact ring 182 is flexedand contact 180 is stressed into firm wiping contact with the resistivefilm or means 16s of the resistance element, that spaced-apart areas ofthe spring wave washer 18w are firmly pressed into good electricalcontact with the step surface s of stud 15 thereby providing anexcellent electrical connection between the stud and contact 180, andthat clutch disc 18d is pressed into firm frictional engagement with theclutch face of wheel 26. Thus, rotation of wormscrew 22 by a suitabletool causes the screw to drive wheel and rotation of wheel 20 results inwiping rotation of contact ring 18r and contact 18c until furtherrotation is stopped by engagement of clutch disc ear 182 with stopproject-ion 14p. Thereafter continued rotation of the screw in the samedirection results in harmless slipping of the clutch face of wheel 20over the clutch disc 18d. During such slippage alternate furthercompression and expansion of wave washer 18w occurs, with slightconcurrent additional flexing of contact ring 1551'. Thereafter,rotation of the worm screw in the opposite direction results in rotationof the Wheel and contact device in the opposite sense. During suchslipping of the clutch members in either direction, the alternatingincrease and decrease of resistance to rotation of the screw furnishes atactile or sensible signal or indication of the .arrestment of thecontact device. Similarly, an audible signal is produced as thedeformations ride over the ridges of the worm wheel clutch face. Thusthe technician adjusting the instrument is advised of the fact that alimit of adjustment has been reached. Further it should be noted thatthe inner end of the wormscrew is at all times securely maintained inthe saddle bearing 14 by force applied to the screw by wheel 20.

Due to the inherent strength of the integral box-like cover member 12,and the nature or construction of the base member and the close fit andpermanent cementing of the inner portion thereof to the cover, theresultant housing is extremely .strong and resistant to mechanicalabuse. The external dimensions of the housing of thecommercially-produced variable resist-or being no greater than 0.25 x0.25 x 0.19", it is evident that wall thicknesses must be held to thefeasible minimum to leave space for the operating parts, and thus theminiatur device would ordinarily ibe housed in a weak structure ifconventional variable resistor housing design practices were followed.As constructed according to the description, the housing is inexpensivebut extremely strong.

As is evident to those skilled in the art, the lengths of the terminalwires may be such as to meet the requirements of the trade. As depictedthe terminal members are adapted to permit mounting of th variableresistor on socalled printed circuit panels or boards.

The preceding description of a preferred physical embodiment of theinvention illustrates how the aforestated objects of the invention areattained. In the light of the description, changes and modificationswithin the scope and spirit of the invention will occur to othersskilled in the art; and accordingly I do not desire that the inventionbe restricted except as defined by the following claims.

I claim:

1. A variable resistor comprising:

a base member of molded electrically insulative material, said basemember including a flat wall-like portion and an integral outstandingportion disposed at a right angle to said wall-like portion;

a rod-like conductive terminal member mounted in said outstandingportion of said base member and having a portion exposed at the exteriorof said outstanding portion;

a conductive stud having a base portion disposed on said outstandingportion of said base and fusionunited to the exposed portion of saidterminal member, whereby to support the stud perpendicularly of saidterminal member and electrically connect the stud to said terminalmember;

rotary means, including a rotary contact device, having a contact,rotatably mounted on said stud and conductively connected therewith;

resistance means, including a resistance element secured to said basemember and disposed to be brushed by said contact and having at leastone terminal;

means, including cover means cooperating with said base member toenclose said rotary means and resistance element for protection of thelatter;

and driver means rotatably supported on said cover means and engagingsaid rotary means for rotating said rotary means, whereby the resistanceexhibited between said terminal and said terminal member is variedbetween limits incident to rotation of said rotary means by said drivermeans.

2. A variable resistor according to claim 1, said rotary means includinga driving means engaging said contact device and engaged by said drivermeans to be driven by the latter means. i

3. A variable resistor according to claim 1, said resistance elementcomprising an apertured insulative plate mounted on said base member andsaid stud, said plate having affixed thereon a generally arcuateresistive means disposed arcuately around said stud.

4. A variable resistor according to claim 1, said rotary means includinga gear wheel member having a set of gear teeth disposed about the axisthereof and a set of clutch elements, and said contact device comprisinga clutch disc having complementary clutch elements engag'ed with saidset of clutch elements, and said driver means comprising a rotary gearhaving bidirectional driving engagement with said set of gear teeth.

5. A variable resistor comprising:

a base member of molded insulation, said base member comprising firstand second integral portions the first of which is a wall-like portionand the second of which is disposed substantially at a right-angle t0the first portion, said first portion having a generally flat exteriorface and an interior face;

an elongate conductive terminal member fixed in said second portion ofsaid base member;

a conductive stud extending upright from said second portion of saidbase member adjacent to said interior face and welded to said terminalmember;

housing means, cooperable with said base member to provide a protectedenclosure around said stud;

a resistance element mounted in said enclosure and having terminal meansextending therefrom to the exterior of said enclosure;

rotary means, including rotary contact means rotatably disposed on saidstud in electrical communication therewith and brushing on saidresistance element;

and means, including driver means rotatably supported on said housingmeans, for rotating said rotary means to vary the resistance exhibitedbetween said terminal member and said terminal means.

6. A variable resistor comprising: 7

a housing including abase member having an exterior face and an interiorface, and a conductive stud upstanding from the interior face of thebase member;

means including a resistance element disposed on said base member aroundsaid stud;

rotary means on said stud, including a contact device including a springwave washer portion riding upon and electrically contacting said stud,said contact device including integral with said washer portion acontact ring having a contact, and said contact device I furtherincluding a ,clutchdisc secured to said contact ring for rotationtherewith, and said wave washer portion serving to stress said clutchdisc away from said interior face and to stress said contact towardsaidresistance element, said rotary means further including a toothedwheel having a clutch face engaging said clutch disc;

terminal means connected respectively to said stud and said resistanceelement and extending to the exterior of said housing;

and rotary driving means accessible from the exterior.

of said housing and engaging said toothed wheel to rotate the latter toyieldingly drive said contact device through said clutch disc and clutchface, Whereby incident to proper rotation of said driving means theresistance exhibited between said terminals is varied.

7. A variable resistor according to claim 6, said contactdeviceincluding a stop means and said housing in cluding an abutment meansdisposed for engagement by said stop means for arresting rotary motionof the contact device, said stop means and abutment means beingconstructed andarranged to limit rotation of said contact device tolessthan 360 of rotation and said contact device when arrested acting toyield and permit continued driving motion of said driving means anddriven movement of said toothed wheel and to provide by alternatelyincreased and decreased resistance to rotation a sensible signalindicative of arrestment of the contact device during further continuedrotation of said driving means.

8. A variable resistor according to claim 6, said housing including awall means having an interior face bearing on said toothed wheel andpressing'the latter into engagement with said clutch disc.

' 9. A variable resistor comprising: I means, including a hollow housingcomprising a base member and a cover member, said base member comprisinga fiat bottom portion, and a stud having a conductive surface, said studupstanding from the fiat bottom portion of said base member;resistanceelement means, comprising a flat Wafer encircling said studand ai'lixed to said base and bearing an insulated arcuate resistanceelement;

rotary means rotatably mounted upon said stud, in-

cluding a contact ring encircling and integral with a wave washer andhaving a contact brushing on said resistance element, said rotary meansfurther including a clutch disc secured to said contact ring and a gearwheel having a clutch face engaging said clutch disc, said wave washerpressing on said stud and providing electrical connection between thelatter and i said contact ring and serving to press said contact ontosaid resistance element and said clutch disc against said clutch face,said cover member preventing movement of said clutch face out of contactwith said clutch disc;

end portions of said resistance element; and driver means supported bysaid first named means for rotating said rotary means. 10. A variableresistor according to claim 9, said clutch terminal means connectedrespectively to said stud and disc comprising radial deformations andsaid clutch face comprising complementary radial deformations.

11. A variable resistor according to claim 9, said clutch disc and saidbase member having cooperable stop-andabutment means eifective to limitrotation of said contact ring to less than 360, and said clutch disc andsaid clutch face comprising cooperating radial deformations, wherebyincident to overturning of said driver means following arrestment ofsaid clutch ring, said clutch ring intermittently yields downwardlytoward said bottom portion and with said gear wheel produces a tactilesignal indicative of such overturning,

12. A variable resistor comprising:

housing means comprising a cover member having a box-like form with fourside walls and an end wall and an opposite open end, and comprising abase member having a bottom portion arranged to lie against the interiorface of one of said side walls and having an upstanding wall portionadapted to closely fit and close said open end of said cover member;

a wormscrew disposed in and across said cover member closely adjacent tothe junction of said end wall and one of said side walls;

operating means, including rotary means, mounted on said base member,said rotary means including a rotatable contact traversable along aprescribed path and means including a gear wheel for rotating thecontact;

a resistance element means disposed in said housing means with aresistive element disposed along and adjacent said track for cooperationwith said contact,

said gear having teeth complementary to the thread of said wormscrew andsaid gearwheel being constructed and so disposed relative to said basemember that insertion of said base member into cover-closingrelationship with said cover member brings said teeth into effectiveoperative relationship with respect to said wormscrew in the absence ofaccurate disposition of the axis of said wormscrew relative to thecenters of the teeth of said gear. 13. Awormscrew-adjusted variableresistor comprising: first means, including a box-like cover memberhaving four sidewalls and an endwall closing one end'and having theother end open; wormscrew 'means mounted in said cover generally 7parallel to said endwall; second means, including a base member havingangularly related first and second portions the first of which isconstructed and arranged to fit the open end of said cover member andwith the cover member form a closed box-like structure and the second ofwhich portions is constructed and arranged to be disposed against theinterior of one of said sidewalls, said second means including rotaryvariable resistor means mounted on said base member and including arotary gear wheel for operating saidvariable resistor means, said rotarygear wheel being disposed for engagement with said wormscrew meansincident to insertion of said second portion of said base member intosaid cover member; and means securing said base member to said covermemberwith said gearwheel and said wormscrew in operativeinterengagement. I 14. A variable resistor according to claim 13,'inwhich said first portion of said base member includes portions abuttingagainst the interior surfaces of the sidewalls of said cover member andincluding a flange portion spaced from the edges of said sidewalls toprovide a groove for reception of adhesive. sealant means, whereby saidgear wheel is maintained in operative relation with said worn1 15. Avariable resistor according to claim 13, said second portion of saidbase member having molded in situ therein a terminal wire, and saidterminal wire having 9 it welded thereto a stud upon which said rotaryvariable redriver member for rotating said wheel member, said sistormeans are supported. second means further including terminal means for16. A wormscrew-adjusted variable resistor comprising: said resistanceelement and aterminal connected to first assembly means, comprisingaround a stationary said stud for electrical communication with saidconconductive stud and in superposed relationship, a 5 tact. stationaryresistance element, a rotary contact device, and a wheel member, saidcontact device com- References Cited y the Examine! prising insuperposed relationship a contact ring en- UNITED STATES PATENTScircling and integral with a wave washer device, and a clutch discconnected to the contact ring to rotate 1O g et a] therewith as a unitand said clutch disc being engaged 2884506 4/59 g by said wave washerand said wave washer contact- 2974299 3/61 Yraus g g' 338 163 ing saidstud, said contact ring comprising a contact 3054077 9/62 ec e a 338 175in brushing relationship with said element, and said 5 10/63 Z e 338 174Wheel member comprising a clutch face in frictional 15 g 11/63 a 0 5 Xcontact with said clutch disc and comprising a toothed 3 /64 5 174portion engaged with a driver member for rotating e or the Wheel member;and RICHARD M. woon, Primary Examiner. second assembly means comprisinga housing enclosing and supporting said first means and including a 20ANTHONY BARTIS, Examiner-

1. A VARIABLE RESISTOR COMPRISING: A BASE MEMBER OF MOLDED ELECTRICALLYINSULATIVE MATERIAL, SAID BASE MEMBER INCLUDING A FLAT WALL-LIKE PORTIONAND AN INTEGRAL OUTSTANDING PORTION DISPOSED AT A RIGHT ANGLE TO SAIDWALL-LIKE PORTION; A ROD-LIKE CONDUCTIVE TERMINAL MEMBER MOUNTED IN SAIDOUTSTANDING PORTION OF SAID BASE MEMBER AND HAVING A PORTION EXPOSED ATTHE EXTERIOR OF SAID OUTSTANDING PORTION; A CONDUCTIVE STUD HAVING ABASE PORTION DISPOSED ON SAID OUTSTANDING PORTION OF SAID BASE ANDFUSIONUNITED TO THE EXPOSED PORTION OF SAID TERMINAL MEMBER, WHEREBY TOSUPPORT THE STUD PERPENDICULARLY OF SAID TERMINAL MEMBER ANDELECTRICALLY CONNECT THE STUD TO SAID TERMINAL MEMBER; ROTARY MEANS,INCLUDING A ROTARY CONTACT DEVICE, HAVING A CONTACT, ROTATABLY MOUNTEDON SAID STUD AND CONDUCTIVELY CONNECTED THEREWITH; RESISTANCE MEANS,INCLUDING A RESISTANCE ELEMENT SECURED TO SAID BASE MEMBER AND DISPOSEDTO BE BRUSHED BY SAID CONTACT AND HAVING AT LEAST ONE TERMINAL; MEANS,INCLUDING COVER MEANS COOPERATING WITH SAID BASE MEMBER TO ENCLOSE SAIDROTARY MEANS AND RESISTANCE ELEMENT FOR PROTECTION OF THE LATTER; ANDDRIVER MEANS ROTATABLY SUPPORTED ON SAID COVER MEANS AND ENGAGING SAIDROTARY MEANS FOR ROTATING SEAID ROTARY MEANS, WHEREBY THE RESISTANCEEXHIBITED BETWEEN SAID TERMINAL AND SAID TERMINAL MEMBER IS VARIEDBETWEEN LIMITS INCIDENT TO ROTATION OF SAID ROTARY MEANS BY AID DRIVERMEANS.